1. Field of the Invention
The present invention relates to a color liquid crystal display panel capable of displaying color pictures and, more particularly, to a liquid crystal display panel of color-filter-on-array construction (COA construction) having a pixel electrode substrate provided with pixel electrodes, thin-film transistors (TFTS) and a color filter layer.
2. Description of the Related Art
A conventional color liquid crystal display panel of COA construction has a pair of electrode substrates, i.e., a pixel electrode substrate and a counter electrode substrate, a liquid crystal layer held between the pair of electrode substrates, and a color filter layer formed on the pixel electrode substrate provided with pixel electrodes and TFTs. In the pixel electrode substrate of this color liquid crystal display panel of COA construction, the TFTs, the color filter layer and the pixel electrodes are stacked in that order on a glass substrate.
Referring to FIG. 6 showing a conventional pixel electrode substrate 1 in a schematic plan view, a gate line 11 and a signal line 12 are formed perpendicularly to each other on the glass substrate. A TFT 20 is formed on the glass substrate at a position near the intersection of the gate line 11 and the signal line 12. It is noted that the pixel electrode substrate 1 is provided with a plurality of gate lines 11, signal lines 12 and TFTs 20 (refer to FIG. 3 associated with the present invention); however, only one unit of arrangements of the pixel electrode substrate 1 is shown in FIG. 6.
As shown in FIG. 6, each TFT 20 has a gate electrode 21 laterally extending from the gate line 11, and a drain electrode 22 laterally extending from the signal line 12. A color filter layer (color layer) 16 and pixel electrodes 13 are stacked in that order on the TFTs 20 (refer to FIG. 2 associated with the present invention). The pixel electrodes 13 and the color segments of the color filter layer 16 form stripe-shaped color regions. The color filter layer 16 has red color segments (R color segments), green color segments (G color segments) and blue color segments (B color segments). The R, the G and the B color segments are arranged successively in a direction parallel to the gate lines 11 (refer to FIG. 3 associated with the present invention). Protective strips 18 are interposed in regions each extending between the adjacent color segments of the color filter layer 16, respectively.
Incidentally, the pixel electrodes 13 and the color segments of the color filter layer 16 must be formed as close to the signal lines 12 and the gate lines 11 as possible to provide the liquid crystal display panel with a high array aperture ratio. Therefore, the TFTs 20 are formed in stripe-shaped color regions as shown in FIG. 6.
In this conventional liquid crystal display panel, however, since the pixel electrodes 13 are connected to the TFTs 20 in the stripe-shaped color regions, contact holes 15 must be formed in parts of the color filter layer 16 between the pixel electrodes 13 and the TFTs 20 or the color filter 16 must be formed so as to extend around the source electrodes of the TFTs 20, which requires precision processing techniques and advanced alignment techniques. The color filter layer 16 can be formed by a printing method. For example, a color pattern formed on a predetermined base may be transferred to the glass substrate by a gravure printing method. However, the color pattern to be transferred to the glass substrate must be provided with holes corresponding to the contact holes 15, and the holes of the color pattern must be correctly aligned with the contact holes 15 formed on the glass substrate when transferring the color pattern to the glass substrate, which requires a precision alignment technique.